1. Field of the Invention
This invention refers to an apparatus for integrating an optical character generator into a printer housing.
2. Description of the Related Art
The integration of optical character generators of non-mechanical printers in a corresponding printer housing is always accompanied by adjustments. The necessity for such adjustments is thereby explained based on the fact that the optical images generated by the character generator are projected onto a transfer printing drum through an imaging optics. The typical imaging scale of imaging optics that are employed lies at a ratio of 1:1. Since the imaging optics is preferably integrated fixed in the character generator, the distance of the surface of the imaging optics from the surface of the transfer printing drum must be optimally set so that the imaging quality is not inadmissably deteriorated by transgressing the depth of field of the imaging optics. Assuming that the character generator can be manufactured rather precisely, the setting of this distance, however, is greatly dependent on how exact the distance between the seating point of the character generator in the printer housing and the rotational axis of the transfer printing drum can be set. This setting precision is deteriorated by a statically changing untrue spindle running of the transfer printing drum. Since this untrue spindle running cannot be avoided, the depth of field of the imaging optics constantly varies within a certain range of tolerances. So that the quality losses are not further increased when imaging the optical images onto the surface of the transfer printing drum, the distance between the seating point of the character generator in the printer housing and the rotational axis of the transfer printing drum should be kept constant. This, however, the device including proves problematical when the character generator, for example in case of maintenance, is taken out of the printer housing and is then subsequently reintroduced thereinto.
A possibility of avoiding the problem is conceivable in that the distance is again re-adjusted after every integration of the character generator into the printer housing. What is especially disadvantageous given this type of procedure is that an individual adjustment error possibly deriving from constant adjustments will additionally deteriorate the imaging quality.
WO 88/00 739 discloses a fastening and setting mechanism for the exact arrangement of a character generator relative to a light-sensitive surface. What are characteristic of the fastening and setting mechanism are, first, a plurality of fixing or, respectively, locking elements with which a light emission arrangement arranged on a carrier element at both long sides of the character generator is detachably secured at a prescribed spacing from the light-sensitive surface. Over and above this, on the other hand, fastening and adjustment elements are also provided on the carrier element with which an imaging optics of the character generator can be adjusted between the light-sensitive surface and the light emission arrangement for an optimum imaging characteristic, for example resolution and depth of field of the latent electrostatic image on the light-sensitive surface.